random/1

Hi,
why random/1 dont work on Version 5.5.38 ?

the reference exist in help : 
random(+IntExpr)
    Evaluates to  a random integer i for which 0=< i< IntExpr.  The seed
    of  this random  generator is  determined by the  system clock  when
    SWI-Prolog was started.

25 ?- random(100).
ERROR: Undefined procedure: random/1
26 ?- 

  Cheers,

jf dazy